This invention relates to an improved composite product having a low-porosity support layer and the method of manufacture thereof. More particularly, this invention relates to an improved composite product and an improved process for the manufacture thereof comprising a layer or substrate of a low-porosity material, such as asbestos, and intended to serve as a floor covering product.
In particular, this invention improves the bond strength and delaminating resistance of a sheet of a low-porosity material, such as asbestos, present as in internal layer in a floor covering product.
In the floor covering market a certain number of products are known and available which include a layer, generally of asbestos, which serves as a support for various PVC plastisol coatings and ink printings combined in a known manner to obtain a finished product. If this support layer is sandwiched between two plasticised PVC sheets (as is typical in construction of this type), it has been found that the bond strength between the plasticised PVC sheets and the support layer is poor in the contact zone between those sheets. It has been found that it is possible to completely delaminate products of this type at low force or stress levels. Tests have shown that a force as low as 0.08 kg(1.73.times.10.sup.-3 W) per cm. width of material is sufficient to effect delamination in these prior art products. This delamination presents a serious problem and drawback to the utility of these floor covering products. Experience shows that bond strengths of at least ten times greater than are now generally available (i.e., on the order of 1 kg/cm) are required to insure that the composite material stays together during handling, in particular during laying or installation on floors, and remains together for long periods of use and service.